The present invention relates to a closure cap for a stationary connector of a container, in particular a motor vehicle radiator having an interior cap element, which has a flow connection between the container interior and the container exterior, and a valve arrangement for opening and blocking the flow connection, wherein a valve body, which can be moved back and forth is pushed with a bias in the direction toward the container interior against a seal seat on the interior cap element so that it can lift off the seal seat when a threshold value of the interior pressure in the container is exceeded.
In connection with known closure caps, for example for motor vehicle radiators, the valve body of the valve arrangement is constantly charged in such a way that the flow connection between the radiator interior and the radiator exterior is opened after a defined threshold value of the interior radiator pressure has been exceeded. This then results in the discharge of air interspersed with coolant water. Such simple closure caps provide a pressure equalization during the operation of the motor vehicle at the time when the pressure in the radiator increases, caused by the heating of the cooling water, and a critical pressure value has been reached or exceeded. This is a safety aspect. However, in motor vehicles the overpressure also rises because of residual heat when the vehicle is stopped, i.e. the engine has been shut down, so that in connection with the simple closure cap mentioned a complete opening also takes place and the danger arises that a large amount of cooling water escapes, or evaporates, or the radiator even boils empty, so that cooling water must be frequently replenished. Multi-stage closure caps were therefore developed (DE 41 07 525 C1), which release the overpressure created by the residual heat in other ways than an essentially higher overpressure occurring because of a malfunction. However, such a closure cap is relatively elaborate because of several valve body elements, which can be moved in respect to each other, and because of several sealing and counter-sealing surfaces. Moreover, cooling water is also sprayed out in the course of this pressure relief in case of an overpressure caused by residual heat after the vehicle engine has been shut off. An absolute loss of water can in this case only be prevented if a compensating reservoir for catching the fluid is installed, or an additional recirculating pump is used, which prevents a pressure increase after shut-down by recirculating the coolant. But this is also elaborate.
It is therefore an object of the present invention to provide a closure cap of the type mentioned at the outset, by means of which, on the one hand, an opening in case of overpressure caused by residual heat is prevented in a simple and cost-efficient manner and, on the other hand, it remains assured that the container is protected during further increase in pressure.
To attain this object in connection with a closure cap of the type mentioned at the outset the bias with which the valve body is pressed against the seal seat can be set by means of a drive mechanism controlled by the vehicle operation.
By means of the measures of the invention it has been achieved that it is possible to control the bias of the valve body, for example as a function of the operation of a motor vehicle, in such a way that the closure cap does not open in case of a defined overpressure caused by residual heat. By means of this the discharge of air mixed with cooling water is prevented during this xe2x80x9coperational phasexe2x80x9d. There is no need here for additional components, such as a compensating container or a recirculating pump. The overpressure can be caused by cooling of the vehicle radiator during stops. In spite of this, the closure cap will open during a continued pressure increase beyond a defined safety limit in order not to endanger the cooling system by bursting, occurring leaks, also in connecting hoses. For example, the bias can be set in two stages, i.e. to an opening pressure corresponding to normal operations, and a higher opening pressure, which takes into consideration the pressure increase through residual heat. The setting of the bias for the valve body can take place in that the drive mechanism for biasing the valve body is vacuum-controlled, or in that the drive mechanism for biasing the valve body is electro-thermally controlled in different ways. If the bias is controlled by vacuum, the control value can be picked up directly from the engine compartment of spark ignition engines, or Diesel engines. If, however, an electrical signal is provided, it can be directly derived, for example from the operating state of the ignition.
Exemplary embodiments in regard to the mechanical biasing of the valve body ensue in that on the side facing away from the drive mechanism, the valve body is biased by means of a spring, or in that on its end facing away from the valve body the spring is supported on a pressure member, which is axially movable by means of the controlled drive mechanism.
The drive mechanism itself can be embodied in various ways, such as the controlled drive mechanism has an element, which transfers the drive motion to the pressure member, the drive mechanism is constituted by an arrangement, which has a spring-loaded diaphragm, whose axial movement biases the valve body, or the drive mechanism has an element which can be expanded by heat and is arranged axially flush with the pressure member show by way of examples. While in the first case a mechanical piston reacting to a vacuum is provided, and in the second case a diaphragm arrangement which can be moved by a vacuum, in the third case an electric drive mechanism in the form of an electrically heatable expansion element is provided.
Embodiments regarding the individual types of drive mechanisms ensue when the controlled drive mechanism is constituted by a piston-cylinder unit, whose piston is maintained between two springs at the ends and is provided with a ramp facing the pressure member, with a roller element arranged between the ramp of the piston and the pressure member, or when the pressure member is clamped, axially movable, by means of the diaphragm between the exterior element and exterior thread element and is biased by means of a compression spring supported on the handle, with a vacuum-controlled drive mechanism which can be or is connected with a hose leading to the engine, or when the drive mechanism has an element which can be expanded by heat and is arranged axially flush with the pressure chamber, the drive mechanism constituting an electrically heatable expansion material element, or an electrically heatable sorption actuator, preferably a metal hydride actuator, with the drive mechanism being provided with a PCT heating element, or when the drive element has a bellows in which the element which can be expanded by heat is arranged.
The handle is provided with a fixed hose connection element so that a fixed connection between the vacuum hose and the closure cap is provided. It is advantageous to design the release from, or screwing on, of the closure cap on the container connector in accordance with a ratchet-like rotary connecting device is provided between the handle and the exterior thread element, which can be set as a function of the direction of rotation, or in that the ratchet-like rotary connecting device is axially arranged, or in that the ratchet-like rotary connecting device is radially arranged or in that the ratchet-like rotary connecting device has a coupling bolt, which is maintained resiliently movable in its axial direction in a recess of the handle, or in that one side of the end of the coupling bolt which enters into the exterior thread element is provided with an inclined face and can be rotated in its recess, preferably over an angle of +/xe2x88x92180xc2x0, or in that the coupling bolt is connected, fixed against relative rotation, with a rotary lever, or in that the exterior thread element has a collar with bores, which can be engaged by the coupling bolt.
In a further embodiment, characterized in that a torsion protection device, which is controlled as a function of temperature, is arranged between the handle and the exterior thread element, or characterized in that the torsion protection device has a hoop, which is connected to move together with the drive mechanism and has end fingers which penetrate into the cutouts of the exterior thread element, or characterized in that the hoop is coupled to move together with the bellows of the drive mechanism, or characterized in that the bellows is acted upon by a spring, or characterized in that the torsion protection device is integrated into the ratchet-like rotary connecting device the closure cap is connected with a torsion protection device controlled as the function of temperature which prevents the closure cap from being unscrewed from the container connector in an operating state of too high a temperature.